内养生混凝土的强度发展规律及其机理探讨

Research on the strength development of concrete internally cured by super absorbent polymer and the mechanism

研究了不同掺量内养生材料(SAP)对混凝土力学性能的影响,并采用X射线衍射、水化热测量、SEM等方法探讨了其影响作用机理。结果表明,SAP可延缓水泥的早期水化进程,其延缓程度随SAP掺量的增大而增大。掺入SAP后,水泥浆体的主要水化产物未有明显变化。在浆体微观结构中,SAP的释水行为一方面可为周围未水化水泥相提供水源,另一方面其塌陷留下的孔洞可为钙矾石生长提供足够的空间。因此,依靠后续生成的钙矾石可在一定程度上填充SAP留下的孔洞,并产生一定的膨胀作用,从而有助于混凝土后期强度的改善。本试验中,随SAP掺量增加混凝土早期抗压强度略有下降;后期抗压强度呈先增加后减小的变化趋势。当掺入0.15%SAP时,混凝土的抗压强度和抗拉强度最高。

The effect of different contents of super absorbent polymer(SAP)on the mechanical properties of concrete was studied,and the influence mechanism was discussed by X-ray diffraction,isothermal calorimetric and scanning electron microscope.The results show that SAP can retard the early hydration of cement.With increasing dosage of SAP,the retardation degree tends to increase.In the presence of SAP,the main hydration products of cement have no obvious change.On the one hand,SAP can provide water for the surrounding cement clinker phase,and on the other hand,the holes left by SAP can provide enough space for ettringite growth.Therefore,ettringite can fill the holes and produce certain expansion effect,which is helpful to improve the long term strength of concrete.In the study,with increasing dosage of SAP,the early strength of concrete decreases slightly.Whereas the later strength tends to increase up to the optimum dosage of SAP and declines at even higher dosage.The value of strength is the highest when the dosage of SAP is 0.15%.